A solar module operates to convert energy from solar radiation into electricity, which is delivered to an external load to perform useful work. A solar module typically includes a set of photovoltaic (“PV”) cells, which can be connected in parallel, in series, or a combination thereof. The most common type of PV cell is a p-n junction device based on crystalline silicon. Other types of PV cells can be based on amorphous silicon, polycrystalline silicon, germanium, organic materials, and Group III-V semiconductor materials, such as gallium arsenide.
The solar module industry is relatively cost sensitive, and the high cost of starting silicon wafers is one of the key challenges associated with conventional solar modules. Attempts have been made to reduce the amount of silicon through the use of thin slices or strips of silicon. In particular, micromachining operations can be performed on a silicon wafer to form numerous silicon slices, each of which can be further processed to form a PV cell. In forming PV cells, each silicon slice can be rotated by about 90°, thereby yielding a gain in overall active surface area relative to a starting silicon wafer. The use of silicon slices allows a significant reduction in silicon consumption, which, in turn, allows a significant reduction in manufacturing costs of solar modules.
While the use of silicon slices provides the advantages noted above, the resulting solar modules typically suffer limitations on the ability to efficiently convert solar radiation into electrical energy. The inability to convert the total incident solar energy into useful electrical energy represents a loss or inefficiency of the solar modules. One significant loss mechanism typically derives from a mismatch between an incident solar spectrum and an absorption spectrum of PV cells. In the case of a PV cell based on silicon, photons with energy greater than a bandgap energy of silicon can lead to the production of photo-excited electron-hole pairs with excess energy. Such excess energy is typically not converted into electrical energy but is rather typically lost as heat through hot charge carrier relaxation or thermalization. This heat can raise the temperature of the PV cell and, as result, can reduce the efficiency of the PV cell in terms of its ability to produce electron-hole pairs. In some instances, the efficiency of the PV cell can decrease by about 0.5 percent for every 1° C. rise in temperature. In conjunction with these thermalization losses, photons with energy less than the bandgap energy of silicon are typically not absorbed and, thus, typically do not contribute to the conversion into electrical energy. As a result, a small range of the incident solar spectrum near the bandgap energy of silicon can be efficiently converted into useful electrical energy.
It is against this background that a need arose to develop the solar modules and related methods described herein.